In modern spark plugs, seals or sealing elements are used at different locations of the spark plug in order to ensure that the spark plug installed in the engine block or in the spark plug bore is gas-tight with respect to the gases present in the combustion chamber. In addition to an external seal for sealing the transition from the spark-plug housing to the spark-plug bore, at least one internal seal is provided, which is also referred to as internal sealing disk or internal sealing ring, which seals the gap between the housing and insulator.
Due to the specific demands, such as temperature resistance and deformability, imposed on a spark plug seal and in particular on the internal seals, metal seals such as seals made from steel or copper or aluminum are employed in spark plugs. The internal seal is meant to seal the gap between spark-plug housing and spark-plug insulator in a reliable manner across the entire temperature range of approximately −40° C. up to approximately 350° C. to which the spark plug is exposed.
It is an object of the present invention to provide spark plugs that have an improved sealing effect.